Machining fluid



Patented Dec. 18, 1951 MACHINING FLUID Franklin Veatch and John G. Partch, Cleveland, Ohio, assignors to The Standard Oil Company, Cleveland, Ohio, a corporation of Ohio No Drawing. Application March 31, 1948, Serial No. 18,294

2 Claims.

The present invention relates to a novel composition of matter comprising a machining lubricant of the emulsifiable type having a high sulfur content and exhibiting many of the desirable properties of sulfurized cutting oils, as well as to emulsions thereof with water.

In cutting operations in which a good finish is the primary requirement it is the general practice to use an oil. Lubrication between the tool and the work is essential if the cutting operation is to be smooth and even, if the work is to have a good surface finish and the tool life is to be maintained. Inasmuch as the finish, obtained in such work is the primary requirement, it is necessary to operate at relatively slower speeds so that the heat generated during the cutting operation does not become a problem.

In connection with such a cutting oil it is known that the inclusion of sulfur in the oil in an active form improves the oil for cutting purposes, that is, a smoother finish is obtained. It is also known generally that the cutting ability of an oil type machining fluid improves to some extent with an increase in concentration of sulfur and is therefore dependent to some extent upon the concentration of sulfur in the oil. However, because of the numerous difficulties encountered in the sulfurization of a cutting oil and the tendency of ordinary oils to become very black as the sulfur content increases, most cutting oils that have hitherto been available contain generally no more than about 5% sulfur. In fact for many ordinary jobs there is no point in going beyond this amount of sulfur.

In high speed cutting operations where the surface or finish is not important the primary requirement is one of cooling, because the large amount of heat generated by the action of the tool in cutting away the metal at the high speed must be dissipated. Water is the best known medium for dissipating the heat generated at high speed cutting operations. Water, however, accomplishes a minimum of lubrication at the point of contact between the tool and the work.

It has already been proposed to attempt to use the lubricity of oil with the superior heat absorbing properties of water in the form of an emulsion useful in metal machining operations. Such an oil may be an ordinary hydrocarbon oil and an emulsifying agent so that upon the addition of the oil to water a stable emulsion is formed. Such oils, strictly speaking, are emulsifiable in water although they are commonly known in the art as soluble cutting oils and may be referred to hereinafter by this name.

These soluble oils are very light colored emulsions of a white to light creamy nature and are desirable for this reason. Emulsions of this type are a slight improvement over water alone because the lubricity attributable to the oil in the emulsion does obtain a slight beneficial effect. However, they leave much to be desired from a libricity standpoint and are not at all com-- parable with a cutting oil. Such emulsions are used for high speed rough work where surface finish, is not a prime requirement and where cooling is the principal requirement. That such emulsions add little to the lubricating action can be seen from the fact that emulsions generally contain a high proportion of water, generally not less than More than this would interfere with the heat dissipating aspect of the soluble cutting oil which is the prime requirement. This small proportion of oil is relatively ineffective in providing lubricationespecially when it is considered that the emulsions are of the oil-in-water type in which the oil is in the inner phase and the outer water phase is much more apt to come in contact with the tool and the work.

It has also been proposed to include a small amount of a sulfurized base in a soluble cutting oil. Tests and experience have shown, however, that inclusion of small amounts of sulfur does not noticeably eifect the character of the finish. For instance, if a sulfurized cutting oil containing 2% to 3% sulfur is emulsified with water in a 5% emulsion the total amount of sulfur in the emulsion is only a very small fraction of one per cent. This has been found in practice to be of no substantial advantage over the ordinary nonsulfurized soluble oils. Accordingly there is no point in using the more expensive sulfurized cutting oil in compounding a soluble oil. Furthermore, since the ordinary sulfurized oils are dark to black in color, the emulsions are very brown as compared with the light emulsions of ordinary soluble cutting oil.

That the presence of the small amount of sulfur in a soluble cutting oil is of no advantage is confirmed by tests of products on the market which are the so-called E. P. soluble oils which contain up to 3% of chlorine or 3% of sulfur or both. These have been tested in emulsions and compared with an emulsion of an ordinary soluble cutting oil not containing chlorine or sulfur. As a group these commercial chlorinated or sulfurized soluble oils are no better than anordinary soluble oil for the general run of machining operation which require an emulsion for effective cooling of the tool and work.

It has now been found, in accordance with the invention, that a sulfurized concentrate containing at least about sulfur and preferably about to sulfur can be emulsified with water in the usual amount in which an ordinary soluble cutting oil is added to water and that the resulting-emulsion has desirable properties heretofore characterized by an emulsion in that it has high heat dissipating ability, and also that the emulsion produces a finish on the Work com parable with the cutting oils. Thus it is possible in accordance with the invention to obtain at higher speeds the desirable finish which. was characteristic of the low speed operations with cutting oils, or in other words, that the characteristic good finish on the work with a cutting oil can now be obtained at the high speed with an emulsion made in accordance with the invention.

One advantage of the soluble cutting oil of this invention is that emulsions of water therewith are. far superior in cutting. ability to emulsions that have hitherto-been available.

An; advantage of the soluble cutting oil of this, invention, when, it is formed from a sulfurized concentrate having a color suitability index below about 75, is that despite its high sulfur content, the emulsion formed therewith has a light color characteristic of the prior art non-sulfurized soluble oils.

Other advantages of the soluble cutting oil of this invention are that when an emulsion thereof with water is used in machining metals, it gives a surface finish, under high speed conditions, approaching that obtained by the use of sulfurized mineral cutting oils, and is capable of more: effectively removing the'heat generated by the: operation.

Still other advantages. of the present invention are that it provides a cutting oil emulsion that is: stable and considerably less expensive than cutting. oils of equal cutting ability.

' Thehighlysulfurized soluble cutting oil of the invention is composed of the sulfurized concentrateandi an emulsifier; The sulfurized concentrate should contain at least 15% and preferably as. high as 35% to 50% sulfur. It may be prepared by reacting elemental sulf ur with an olefinic material such as the highly branched olefini'c polymer known generally in the petroleum industry as motor polymer.

The term motor polymer, as hereinafter used in the specification and claims, is'a polymer made from C3 and C4 olefins by non-selective polymerization, e. g., with a phosphorus acid type catalyst. It is a slightly fluorescent, light colored liquid having an E2 clear octane rating in the range of -85. It has a typical motor gasoline boiling point range with the bulk of the products boiling off at between about and 360- FR, thus indicating that the bulk of the material is in the (Ia-C10 olefin boiling range with some lighter and heavier ends. The polymers appear, in general, to be fairly highly branched and contain substantial proportions of tertiary olefins. Little or no di-olefins are present and it contains virtually no aromatic, naphthenic or paraffinic constituents. This is well known in the industry as motor polymer and need not be further defined to be fully understood by one skilled in the art. It is to be distinguished from cracked products or unsaturates extracted from cracked products.

A polymer gasoline fraction may be removed from such a motor polymer by fractional distillation to the 250 F. cut point, and the residue is known as reduced motor polymer. The reduced motor polymer may contain small amounts of materials lighter than trimer, its average molecular weight is about 145, and it preferably contains a major amount of olefins boiling below 600 F.

Although it has been found that it is possible to obtain a stable sulfurized concentrate having the required high concentration of sulfur by using motor polymer as such, it is to be understood that the reduced motor polymer described herein is included within the term motor polymer.

The sulfurized concentrate may be prepared by placing the sulfur and motor polymer in a closed vessel and heating the components to a temperature between about 250 and 300 F., and not exceeding 350 F., for several hours depending upon the concentration of sulfur desired in the final product. If desired, the reaction may becarr-ied out in the presence of a diluent, such as. hexaneor a paraffin oil.

Inasmuch as: the reaction may be. carried out in a closed vessel in the preferred embodiment and a. considerable proportion of the motor polymer boils at a temperature below the temperature to which the reaction products, are raised, pressures of about 70-100 or more pounds per square inch are developed during the reaction. It is be,- lieved that the reaction mixture is two phase in the-early stages of the process but that it becomes single phase as the sulfur reacts. Little or no hydrogen sulfide is produced.

It is preferable, but by no means necessary, to stir the reaction mixture mildly during the reaction to. insure even heat distribution. When the reaction is carried out in the presence of hydrogen sulfide, the HzS may be present in concentrations up to 25 and 30% or more. Concentrations, as low as 2%, however, have been found to be quite effective as will appear from the examples herein.

Although the time of reaction may vary considerably depending upon the concentration of sulfur desired in the concentrate and upon the temperature of the reaction, it is desirable to carry out the reaction at least until about 30% of stable sulfur-motor polymer product is formed. It has been. found that optimum results are obtained by heating the reaction mixture for a period of from about four to about six hours. The temperature of the reaction may likewise varyconsiderably within the limits specified herein, temperatures within the neighborhood of 300 F. being preferred.

When the reaction mixture has been heated for the prescribed period of time, it is allowed to cool. The reaction mixture is then preferably subjected to stripping or fiash distillation to recover any unreacted olefin from the sulfur-motor polymerconcentrate and cooled and settled or filtered to remove any unreacted sulfur.

In steam stripping, the reaction product is placed in a suitable vessel provided with means for introducing and removing the distillate. Steam, at a temperature of about 260-275 F., is forced through the reaction mixture and thereby picks up the volatile components, 1. e., the unreacted olefins, if any, and carries them with it through the vessel, a condenser and into a receiver where two layers, water and unreacted motor polymer, are separated. The water may be vaporized and recycled through the steam stripping apparatus and the motor polymer is recovered and used again in the sulfurizing process.

An alternative method of recovering unreacted motor polymer from the sulfur-motor polymer concentrate involves flash distillation wherein the reaction mixture is introduced continuously into a vessel'heated to about 300 F. and preferably maintained at sub-atmospheric pressure.

The volatile components are immediately flashed 01f while the sulfur-motor polymer concentrate is continuously withdrawn from the bottom of the vessel. The time during which any portion'of the sulfur-motor polymer concentrate issubjected to this temperature is only about two or three minutes, depending upon the size of the vessel.

While the steam stripping method is preferred,

it is to be understood that flash distillation and other forms of distillation can be employed without departing from the scope of this invention.

' The sulfur-motor polymer concentrate thus formed has an unusually and desirably low color suitability index. This is 75 or less and as a result the concentrate gives emulsions which are light in color and comparable with emulsions of ordinary soluble cutting oils. The expression color suitability index is the ratio of the optical density to the sulfur content of the concentrate. The term optical density represents the standard logarithmic ratio of intensity of an incident light ray falling on a transparent or translucent medium to the intensity of the transmitted ray for a sample length of one meter and light of a wave length of 5100 to 5500 Angstroms.

Any surface-active emulsifying agent may be used in accordance with the present invention in a quantity sufiicient to form a permanent emulsion with water without requiring very much agitation. This quantity depends upon the char- 1".

agent can be used. Its action is physical and its function well understood.

In addition to the emulsifying agent, the ma chining fluid of this invention may also contain a lubricating oil, such as, for example, a stra oil. The lubricating oil assists in forming a stable emulsion but can be omitted from the composition if the sulfurized concentrate and the emulsifying agent alone are capable of emulsifying with water and remaining in a stable emulsified form therewith.

The machining fluid, comprising an emulsifier in an amount forming a ermanent emulsion with water, a sulfurized concentrate having at least sulfur and, if desired, minor proportions of a lubricating oil, may be added to water in an amount of from about 1 to preferably about 5 to 10%, to form a stable emulsion therewith. The machining fluid need merely be dumped into the water and forms, with ver little agitation, a permanent emulsion that is generally yellowish in color. The emulsion lasts as long as the oil does and it is circulated over the metal and the cutting tool employed in the machining operation. The large water content of these emulsions gives them a high cooling capacity.

Without intending in any way to limit the scope of the present invention, the following specific example is included to supplement the disclosure herein.

steel containing .10%

6 Example 44 pounds of motor polymer and 36 pounds of sulfur were heated in a closed reaction vessel to a temperature of 300 F. for five hours while agitating the vessel slightly to stir the contents.

It was found that the reaction mixture contained 32% by weight of sulfur. Unreacted sulfur was removed and 28.7% by weight of the unreacted product was removed by steam stripping to yield a sulfur-motor polymer concentrate characterized by the following data:

Percent sulfur. 4413 Color Amber to brown Optical density 1377 Color suitability index 30.7

Density at 20 C 1.094

Refractive index (at 20 C.) 1.5835

Viscosity at 100 F. SUS 270 Molecular weight Approx. 400

The percentage of yield, corrected for recovered sulfur and olefin, was and the sulfur-motor polymer product was found to be a stable liquid.

2 parts by weight of the sulfur-motor polymer concentrate thus prepared were mixed with 2 parts by weight of a straw oil having a viscosity SUS at 100 F. of 75, and 1 part by weight of a sulfonated mineral oil to form a sulfurized water soluble cutting oil having 17.9% sulfur, which is referred to as soluble oil A. 5 parts by Weight of this mixture were mixed with parts by weight of water to form a 5% test emulsion.

Emulsions of soluble oil A and two other well known commercial soluble oils available on the market were subjected to severe surface finish tests on a heavy lathe. In each test the test piece was AISI C 1010 Steel BHM 77 (American Iron and Steel Institute, open hearth carboncarbon and having a Brinell hardness number of 77, no alloy present), hot rolled and fully annealed. The tool used in each test was an 184-1 H55 (18% tungsten, 4% chromium and 1% vanadium high speed steel) single point tool having a back rake and side rake of 0, an end relief, side relief and end cutting edge of 7. a side cutting edge of 15 and a nose radius of of an inch. The depth of cut in each test was 0.25 inch, the feed was .0025 inch per revolution of the work piece, and each test was conducted for a minimum of 15 minutes to machine an area large enough to be analyzed easily with a Brush surface analyzer conveniently used for this purpose. The finish was in each instance measured bothperpendicular and parallel to the feed, giving peak-to-valley and root means square values. Two peak-to-valley and two root mean square values were obtained for each test and averaged. Finally the ratio of each of these values to one another were computed. The lower the figure, the better the finish.

The following table shows the results obtained under the severe finish testing conditions described. The surface finish index of each fluid being determined at a cutting speed of 40 surface feet per minute.

This shows that the sulfurized soluble cutting oil of the invention is far superior to the two commercial soluble oils tested especially in view of the fact that one of these were tested in a 10% emulsion rather than the 5 emulsion in accordance with the invention, and therefore would be expected to have a lower surface finish index.

The surface finish index of an ordinary nonsulfurized cutting oil is included for comparison and it is of the same order as the ordinary soluble oils. A test with sulfurized oil having the same amount of sulfur (0.89%) as the emulsion on the same steel was not available for comparison. The surface finish index of a sulfurized cutting oil having 3.3% sulfur is included, however, and while this gives a somewhat superior surface finish it contains almost four times as much sulfur as the emulsion and would be expected to give a much better finish for this reason. It also does not have the heat removing capacity.

From this it will be seen that the emulsion of the invention is superior to an ordinary oil and that the emulsion containing the same amount of sulfur is about equivalent to or approaches a cutting oil containing the same amount of sulfur. This demonstrates what has been described previously, namely, that about as good a finish can be obtained with the emulsion as with an oil with an equivalent amount of sulfur, plus the high heat removing ability and the high surface speeds that are permitted.

It is believed that this unusual ability of the soluble oil of the invention to obtain excellent finishes is due at least in part to the character of the sulfurized concentrate, that is, the sulfur is present as a reaction product with an olefinic material, and is to be distinguished from other characteristics of sulfurized bases in which the sulfur is reacted with other types of chemical compounds or hydrocarbons and is therefore present in other forms.

It is to be understood that innumerable variations and modifications will immediately become apparent to those skilled in the art upon reading the foregoing disclosure. The invention contemplates all such variations and modifications as come within the scope of the appended claims.

We claim:

1. A machining fluid comprising a stable emulsion of from 99 to 75% water with from 1 to 25% of a lubricant, said lubricant consisting of about 20% by weight of a mineral oil sulfonated or sulfated emulsifying agent and about 40 by weight of a mineral lubricating oil, the balance being a sulfur-motor polymer reaction product containing between 35 and sulfur and having a specific gravity at 20 C. of about 1.094, said product being prepared by reacting substantially equal proportions of elemental sulfur and "motor polymer in the absence of water ina closed vessel at a temperature between 250 and 300 F., said lubricant having a specific gravity of approximately equal to that of water whereby the water emulsion is rendered completely stable.

2. A machining lubricant adapted to be added to water in an amount from about 1 to 25% to form a stable emulsion therewith, said lubricant consisting of about 20% by weight of a mineral oil sulfonated or sulfated emulsifying agent, and about 40% by weight of a mineral lubricating oil, the balance between a sulfur-motor polymer reaction product containing between 35 and 50% sulfur and having a specific gravity at 20 C. of about 1.094, said product being prepared by reacting substantially equal proportions of elemental sulfur and motor-polymer in the absence of water in a closed vessel at a temperature between about 250 and 300 F.

FRANKLIN VEATCH. JOHN G. PARTCH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,052,164 Buo Aug. 25, 1936 2,062,652 Hermann Dec. 1, 1936 2,337,473 Knowles Dec. 21, 1943 2,338,829 Werntz Jan. 11, 1944 2,431,010 Zimmer Nov. 18, 1947 

2. A MACHINING LUBRICANT ADAPTED TO BE ADDED TO WATER IN AN AMOUNT FROM ABOUT 1 TO 25% TO FORM A STABLE EMULSION THEREWITH, SAID LUBRICANT CONSISTING OF ABOUT 20% BY WEIGHT OF A MINERAL OIL SULFONATED OR SULFATED EMULSIFYING AGENT, AND ABOUT 40% BY WEIGHT OF A MINERAL LUBRICATING OIL, THE BALANCE BETWEEN A "SULFUR-MOTOR POLYMER" REACTION PRODUCT CONTAINING BETWEEN 35 AND 50% SULFUR AND HAVING A SPECIFIC GRAVITY AT 20* C. OF ABOUT 1.094, SAID PRODUCT BEING PREPARED BY REACTING SUBSTANTIALLY EQUAL PROPORTIONS OF ELEMENTAL SULFUR AND "MOTOR-POLYMER" IN THE ABSENCE OF WATER IN A CLOSED VESSEL AT A TEMPERATURE BETWEEN ABOUT 250* AND 300* F. 